You'd need a wiring diagram and written instructions for other crew to understand. See post 20 and/or PM me.
Battery system changes
- Thread starter jmkinsfbay
- Start date
Mr. Murphy says that when you have to abandon your start battery and use the house battery, it will not be at the best of times. Trying to find the tools, access the cables and monkey with them while drifting up on a lee shore..... Much easier, faster, and safer to flip a couple of switches.
Generally, it is better to have one big house battery and a separate smaller start/reserve battery. Why one big house battery and not two? The simple mostly correct explanation is that battery life is in part a function of state of charge and how deep and how often the battery is deeply discharged. The key factor is the percent of discharge. If you have a 100 amphour battery and draw 50 ah out of it you have reached a 50% SOC. however, if you have 2 100 AH batteries in parallel and draw 50 ah out of the bank, the bank will at a 75% SOC. The lower discharge percentage is better for the battery. (Now this is pretty close, there is this Peukert formula that is much more accurate, but this captures the essence.)
A good simple system has one big bank of multiple batteries that are primary and the house batteries. A second smaller battery serves as a reserve/start battery. A battery combiner (ACR) allows both banks to be charged with one charging source and prevents one bank discharging into the other. Switches allow each bank to be isolated and combined as necessary.
Sorry for beating another dead horse
but for goo ness sake, the issue is NOT ever combining them, the issue is to be able to switch them easily WITHOUT USING JUMPER CABLES, so that EITHER one or the other battery can provide service. NOT both when discharging. Why? Because of the link I provided earlier: if one bank is DEAD, the very last thing you ever want to do is combine the dead one with the good one, regardless of which is dead. All that will do is kill the good one, too.
I get it, MS. What I do NOT get is why someone would go to the expense of installing three switches including the DCP when one would do the same thing. IIRC, you have mentioned many times how more connections create more possible points of failure.
I also agree with this sentiment: why have the switches when one will suffice IF THE DCP didn't exist?
You and I have spend decades helping folks out in trying to understand their electrical systems. We have offered the single 1-2-B scenario and the two switch version. Wow, now a three switch version? I ain't gettin' any younger, but I have wiring diagrams for everything on my boat. Why? So I can remember. This configuration makes my head spin. I'd need a bloody checklist just to get the boat started and the stereo turned on.
Sorry, cranky pants day, but it seems simplicity is hard to explain to some folks.
OK, explain the advantages of this arrangement. Please. 'Cuz I just ain't gettin' it. One employs a DCP switch that you have many times said is better for powerboats frequently starting and stopping so as not to lose their electronics but not so good for simple recreational sailboats. Now we employ that DCP and add two more switches. HMM, I'm simply agog!
Oh, and I keep having this issue with COMBINING the banks. I read it as when being discharged, not when charging is present. I'll go back and study, honest, I will.
Like this:
Why is turning two switches easier than turning ONE?!?
I'm all ears on this one.
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Matters of opinions here. If you do not want to switch a live battery to bridge with a dead one, why would you parallel batteries where, when one crashes, it can take the bridged ones right down with it? Everyone has an opinion of their own. See Stu's post 23.
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A battery in a paralleled bank can crash the whole bank in the case of a sudden catastrophic failure. No question there. But those instances are pretty rare. Batteries die from old age and abuse, especially deep discharges and long periods of time in a partial state of charge.
The upside to a paralleled bank is that the depth of discharge is less for any given current draw, a 50ah draw out of a 100 ah battery is 50%, out of a 200 ah bank, it is 25%. Shallower discharge means longer battery life. Of course, if you had a single 200 ah battery the effect would be the same. However, there is the aging back syndrome, a single 200 ah battery would probably weigh in the neighborhood of 200lbs, a single 220 ah Golf Cart battery weighs 65 lbs, much easier on the back when it comes time to move them.
The make a 2 bank system work, it is essential that the banks remain isolated unless they are being charged. That what an ACR does, allows the banks to be isolated unless there being charged. Switches like the 1-2-both switch keep the banks isolated until it is on both and then they are in parallel, which is bad if one battery goes bad. That's why an on-off switch is necessary between the battery bank and the selector switch.
Another way to look at this system is to think of it as a 2 bank system where the banks are not equal in size. Same as the old days with the 1-2-both and 2 group 24 batteries. On my boat I have 2 banks, one a 75 ah Group 24, and the other a 460 ah GC bank. If the GC bank crashes, I can still run essentials off the Group 24 until the big bank can be replaced, but the refrigeration will be gone and I'll have to drink warm beer. Likewise if the small bank dies, I can switch over to the big bank and run everything and still start the engine.
In addition to proper wiring, i.e., being able to isolate the banks and switch sources, the key is to have a good monitoring system so you have an idea about the condition of the batteries. Then you will be less likely to be surprised by when one fails.
Finally, there is the human factor we have all either heard stories of boaters who left the 1-2-both switch on both and killed both batteries or have experimented with this condition ourselves. The 3 switch 2 bank solution that MS posted and I have (almost) implemented reduces this opportunity for this human factor problem.
Let's keep this within the context of the OP who already has two bussed ON/OFF switches plus a third negative switch.. Re-purposing the Beneteau negative switch (which is not ABYC compliant), is the easiest approach to achieve cross over and isolation.. I am not a big fan of the cheap battery switches used by Beneteau & Jenneau & I've seen a few physically melted, and some with over 1V of drop under load, so I generally replace them with Blue Sea switches when ever a customer has large loads eg: inverter or bow thruster.
There is no one single switch solution for every application. This boat does not and never had a 1/2/B....
Please read the "Preface" of my 1/2/B thread.. (grin) I have offered far more than the 1/2/B or the 1/2B with an additional ON/OFF. As I have stated very, very clearly the 1/2/B is NOT my "preferred switching solution".... When I can start from scratch, or when budget is not an issue I rarely turn to the 1/2/B. A 1/2/B, if already installed, can be made to work better, hence the thread, but it is by NO MEANS the be all end all switch configuration.
99.9% of the time = DCP to ON (does not get any simpler than that and it is the only switch visible to occupants)
0.1% of the time = Isolate bad bank with battery compartment ON/OFF switch & set DCP to BOTH
Difficult?
The benefit of the battery compartment hidden switches, in the event of a failure, is the ability to use the positive charging bus to still charge the start/reserve battery. With a 1/2/B you need to leave the alt and all charge sources on the "C" post, we know how much you love that idea (wink) or add an additional switch to achieve this. I am not a big fan of the DCP as a stand alone switch because it can not provide bank isolation. With the addition of two hidden battery compartment ON/OFF switches this keeps the DCP a simple ON/OFF yet creates a system featuring full isolation and the charge bus stays with the bank being used...
If the 1/2/B switch was really simple, it would not need an entire thread....
Stu don't become narrow minded about what works or can work. Look at the diagram and run through all the scenarios and you'll see that diagram is ticking all the boxes including simplicity and full isolation including charge sources.. The DCP is only a poor choice if you install it as a stand alone because you loose the ability to isolate a failed bank. Even then the vast majority of the time it works. It is the 0.1% we are protecting for with the addition of to bank isolation switches. I believe isolation, including charge sources, to be a critical design for cruisers and this is all touched on in the 1/2/B thread and a 1/2/B also requiress an additional battery compartment switch if you desire true isolation including the charge sources....OK, explain the advantages of this arrangement. Please. 'Cuz I just ain't gettin' it. One employs a DCP switch that you have many times said is better for powerboats frequently starting and stopping so as not to lose their electronics but not so good for simple recreational sailboats. Now we employ that DCP and add two more switches. HMM, I'm simply agog!
For world cruisers who want to retain a 1/2/B I install a battery compartment bank isolation switch as shown in the DCP diagram. This is done so the charge bus can move with the banks. It goes;
BANK>FUSE>ON/OFF SW>CHARGE BUS
You can't adequately provide bank and charge source isolation with a single 1/2/B and again, this is covered in the 1/2/B thread. With a 1/2/B and the alt & all charge sources run to the house bank how do we charge the reserve battery when we switch to reserve and isolate the house from charging? The answer is we add another switch so the charge bus can be isolated from the house bank. Again, this is all covered in that thread.
Umm the OP already has TWO switches. Re-purposing the neg switch, which is not ABYC compliant anyway, is often the easiest fix for the Bene factory wiring. You now have a three ON-OFF switch system, which is a great system.Why is turning two switches easier than turning ONE?!?
I'm all ears on this one.
There are also many, many boaters out there, with very poorly wired boats, that result in brown outs and transients when starting who don't want the start and house coming from the same bank. On many boats is usually much less expensive to simply wire in a dedicated start battery.
Just last week I visited yet another Bene that had two AGM house batteries and an cheap auto-parts store start battery. The owner "assumed" the banks were isolated "Start" & "House" but they were not. He was running his start battery and house battery as a single large house bank and discharging both together. He is now temporarily doing everything off house and leaving the start set to OFF until I can get to the solution he decided on....
Reading through this thread, I'm thinking I have a "rat's nest" in my 323. Battery locations are one in front of the engine, which I always thought to be the starting battery. The second is under the aft berth behind the engine.
Everything is wired as it was delivered to me, with house wiring attached to a bus at the aft battery. However, this battery also appears to be the designated starting battery, with a positive cable wired direct to the starter. Now I need to go back and sort this out...
I still can't determine why with both batteries ( identical and the same age) physically disconnected and the boat on the hard from September 2015 with batteries fully charged, until May 2017, that the battery I thought to be the starting battery would be essentially dead (10 volts) while the other maintained 12.75 volts.
Everything is wired as it was delivered to me, with house wiring attached to a bus at the aft battery. However, this battery also appears to be the designated starting battery, with a positive cable wired direct to the starter. Now I need to go back and sort this out...
I still can't determine why with both batteries ( identical and the same age) physically disconnected and the boat on the hard from September 2015 with batteries fully charged, until May 2017, that the battery I thought to be the starting battery would be essentially dead (10 volts) while the other maintained 12.75 volts.
Believe you just answered your question - the dead battery is your house battery. Start batteries if used correctly (rarely) keep a high state of charge and very little cycling so they last maximum long. The other thing going on is that with one battery in a hot engine bay and the other under a berth they have very different charge acceptance and your OEM charger is not temp compensated.
Well, you probably have the always on radio on the dead battery? IIRC, removing the battery cables is suggested- or did you mean you did that, not just the switches off? That is a long time to expect the batteries to be stored. Face it, one battery dead does not mean the entire wiring system is a rats nest. If one survived, that should mean the other may have been a bit defective. If anything, swap the cables on the battery switches to make the front battery to start battery.
Maybe you need to trace cables and ID batteries for what they actually are, not what you "have believed" they are.
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Very good comments, you two. So, Gunni has 4 batt's run in parallel, and Ron20324 has 3 batt's bused together. Because of the many reported battery failures that "shouldn't have happened", I have the phobia that when you connect batteries, you won't have any realistic way of knowing if each and every one is equal and "up to snuff", that is, volt gauges will only be seeing a combination value. If they don't remain of near exact same quality, charge, etc., then your charger is going to charge at either one constant voltage, or at an adjusted voltage based on what the charger "sees". In either case, one or more batteries is/are not getting its/their ideal charge. BTW, Gunni, my boat came with a charger with three separate outputs, each of which takes care of its own battery as needed. Then, Ron20324 asks why even use a disconnect switch for the engine battery. Frankly, I'd not thought of that for the boat, but it does make rather profound sense. Please post any additional comments on this issue. Thanks.
Always a great place to be educated! I have a new to me Beneteau 393 that I've been held up on getting. I feel like I'm missing out on this season but the weather here in the northeast has been horrendous. Because I'm heading to the left coast for the birth of my 6th grandchild I don't expect to see the boat until 7/10.
I have no idea how it's wired but believe it's the standard 2003 factory set up. Can't wait to tinker around. I, surprisingly, can follow this thread and understand the different ways and reasoning behind them but maybe someone can clarify the reasoning of the negative switch to begin with? Just curious!
I have no idea how it's wired but believe it's the standard 2003 factory set up. Can't wait to tinker around. I, surprisingly, can follow this thread and understand the different ways and reasoning behind them but maybe someone can clarify the reasoning of the negative switch to begin with? Just curious!
1) Within the many discussions above, I'm still wondering what people are thinking about having multiple batteries on a single charge circuit. Even if exactly the same age, size, etc., I think that within a year, those batteries will start diverging in quality, and the charger will only be supplying some sort of average or amplified charge. Is it felt that this is insignificant? Thank you.
2) I haven't heard whether or not there are, with new technology, any really good 12v deep cycle batteries.
3) I've decided that I'm going to do my battery wiring as shown in the attached jpeg, talk about KISS. Once again, I realize, is that if both House batteries are switched on, while plugged in at dock, there can be a cross-charge, but signage at my battery switches has so far prevented that.
2) I haven't heard whether or not there are, with new technology, any really good 12v deep cycle batteries.
3) I've decided that I'm going to do my battery wiring as shown in the attached jpeg, talk about KISS. Once again, I realize, is that if both House batteries are switched on, while plugged in at dock, there can be a cross-charge, but signage at my battery switches has so far prevented that.
Attachments
OK, I've been watching this thread and have been afraid to look like a rube by posting, but instead of starting a new thread, I thought I might posit my question here...
On our n-t-m '07 Hunter 27, there's a 1/2/1+2 switch. Right now there's a single grp 27 deep cycle that is used for house and starting our little 15hp Yanmar. It came off our prior Hunter 23.5 because I just bought it last September, and I'm a cheapskate! It replaced the existing grp 24 of unknown age; I seem to recall it was a deep cycle (I also figured it was better for the 23.5 anyway since it's smaller and would fit better in the 23.5, which has fewer demands). I definitely want to add a second battery to extend capacity and thought it opportune since it's pretty much ready to accept one.
I was debating whether to get just a starting battery or to add an identical deep cycle battery on the theory that -- as I was told -- our Yanmar doesn't need that much power to crank, and then I'd have a back-up for house needs when sailing or on the hook. I was going wire it in the same way #1 is wired currently but go into #2 on the switch.
I would plan to use one battery at a time. I'm mindful of the warning not to discharge a deep-cycle battery too far, so I was also thinking I could switch to the back-up well before it goes below, say, 66%. I have ordered two DC analog voltmeters to monitor the charge of each battery.
I have a ProMariner OEM charger/inverter that has outputs for up to 3 batteries, which I thought was smart enough to send charge only where needed. I was going to wire that according to the manual, in the same way #1 is wired. I haven't thought through how the alternator interfaces.
We don't have crazy house needs. There's an electric cooler, not a full-on refrigerator. Chart plotter, depth and speed instruments, and nav lights are all low key. I'm going to switch over all the bulbs in the cabin lights to LEDs.
All this discussion about additional switches is getting me a bit confused. When you switch to 1 or 2, aren't you effectively isolating, or do you have to open the negative side to truly isolate?
In my intended plan, am I running afoul of the ideas in the general discussion here? (Apologies in advance if this question is elemental and off-topic to the thread. No doubt I can find answers in the archives.)
On our n-t-m '07 Hunter 27, there's a 1/2/1+2 switch. Right now there's a single grp 27 deep cycle that is used for house and starting our little 15hp Yanmar. It came off our prior Hunter 23.5 because I just bought it last September, and I'm a cheapskate! It replaced the existing grp 24 of unknown age; I seem to recall it was a deep cycle (I also figured it was better for the 23.5 anyway since it's smaller and would fit better in the 23.5, which has fewer demands). I definitely want to add a second battery to extend capacity and thought it opportune since it's pretty much ready to accept one.
I was debating whether to get just a starting battery or to add an identical deep cycle battery on the theory that -- as I was told -- our Yanmar doesn't need that much power to crank, and then I'd have a back-up for house needs when sailing or on the hook. I was going wire it in the same way #1 is wired currently but go into #2 on the switch.
I would plan to use one battery at a time. I'm mindful of the warning not to discharge a deep-cycle battery too far, so I was also thinking I could switch to the back-up well before it goes below, say, 66%. I have ordered two DC analog voltmeters to monitor the charge of each battery.
I have a ProMariner OEM charger/inverter that has outputs for up to 3 batteries, which I thought was smart enough to send charge only where needed. I was going to wire that according to the manual, in the same way #1 is wired. I haven't thought through how the alternator interfaces.
We don't have crazy house needs. There's an electric cooler, not a full-on refrigerator. Chart plotter, depth and speed instruments, and nav lights are all low key. I'm going to switch over all the bulbs in the cabin lights to LEDs.
All this discussion about additional switches is getting me a bit confused. When you switch to 1 or 2, aren't you effectively isolating, or do you have to open the negative side to truly isolate?
In my intended plan, am I running afoul of the ideas in the general discussion here? (Apologies in advance if this question is elemental and off-topic to the thread. No doubt I can find answers in the archives.)
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This is done all the time, world wide and a recommended practice by every battery manufacturer. Folks only get into trouble when they ignore care of their batteries and push them too far health wise.
If you wire them incorrectly they can and will become out of balance. When wired correctly I see little difference in tested capacity between batteries that have been contiguously wired as a single large bank. I have physically tested, for actual Ah capacity, more lead acid batteries than anyone I know of in the marine field. There are only about 3-5 of us actually doing it but everyone should be... I have two 20 hour test stations running nearly continually and am adding a third shortly.
There are plenty of really good deep cycle 12V batteries in AGM & GEL and in golf cart and better flooded batteries. The Trojan T1275 a very decent 12V deep cycle battery. Any 12V flooded battery that is G 24, 27 or 31 is not really "deep cycle" compared to a golf car level battery or better but for coast cruising can certainly work.. Course there is never any need for using 12V batteries for a house bank when 6V golf car batteries are less expensive and extremely robust....
That would not be a diagram I would suggest or install/wire. Can you explain for us in electrical speak what a "cross charge" is? Let's keep single voltage regulation battery chargers in mind (nearly 98% of them are) and Ohm's law too so we don't attempt to re-write it..
You can keep it simple with your 1-2-Both switch. First step ... get immersed in the discussion on MaineSails site here in SBO. Under "Featured Contributors" go to "Musings with Maine Sail" and go to the thread titled "1/Both/2/Off Switches ...." and read as much of it as you can stand. There is about 12 pages of discussion. You may want to have 2 identical batteries, wired in parallel, to use for your house bank and a separate, smaller battery for your "reserve" bank. You will have greater capacity and longer battery life if you increase from 1 battery to 2 batteries for your house bank. This would be a typical set-up for a coastal cruising, weekender type boat such as yours. This thread is pretty much focused on the system that would be used with the switch that you have, so there really is no need for you to look for any great modifications. There are various ways to configure a battery system, and we all have our preferences. As with anything, there are always pros and cons to every system. Yes, your house bank is suitable for starting your engine. The reserve is simply reserve. Your switch can keep the 2 banks isolated. You can charge both banks without difficulty. You do not have a real need to have a separate "start" battery. Some people prefer to have a separate start battery, but you should really read up on the reasons for it and the system modifications before you feel any compelling reason to do so.